1. Smear some turmeric powder and salt on the cleaned bhetki fish pieces. Heat some mustard oil in a pan and fry the bhetki pieces.
2. Now for making the gravy.In a pan add 1 tbsp mustard oil. Once the oil heats up, add the onion paste. Roast the mixture very well till it browns up. Next add the curd, red chilli powder, turmeric and salt to taste. Add a little water and roast the spices. Once the water dries up add another cup of water and let the gravy simmer.
3. Finally, add the fried fish pieces and the green chillies. Let the fish soak up the gravy.
4. Serve with plain rice.